A US Air Force F-15C Eagle has crashed into the North Sea off the coast of Yorkshire, exacerbating concerns about the presence of US forces on British soil.
In a statement, the US Air Force confirmed the fighter jet crashed at around 9.40am.
The aircraft was from the 48th Fighter Wing based at RAF Lakenheath in Suffolk, it added.
"At the time of the accident, the aircraft was on a routine training mission with one pilot on board," the US Air Force said.
Search and rescue teams are reportedly looking for the aircraft, which is believed to have crashed 74 nautical miles off the East Yorkshire coast.
Colonel Will Marshall, commander of the 48th Fighter Wing, said: "Search and rescue efforts are currently under way, but the pilot of the aircraft is still missing.
"We are extremely grateful for the timely response of our UK counterparts in the support of these recovery efforts and remain hopeful that our Liberty Wing airman will be located and recovered", Colonel Marshall added.
RAF Lakenheath is the largest US Air Force base in England, housing more than 4,000 American personnel. It is also home to the US Air Force’s only F-15 fighter wing in Europe.
This is the third time in nearly six years that US fighter jets based at RAF Lakenheath have crashed, potentially causing a mortal threat to the local community.
In October 2014 an F-15D fighter jet based at RAF Lakenheath crashed in fields near Spalding in Lincolnshire, but the pilot ejected safely.
Exactly a year later (October 2015), a US Air Force F-18 Horner jet crashed on farmland near to the sprawling air base, killing the pilot.